It depends on the server that you are connected to. Since Betternet connects you to the servers around the world randomly, sometimes it is possible to have a slow connection on the Internet. The distance between our servers and your location is one of the most critical factors in your speed connection.
Normally if you disconnect and then re-connect the app, you could connect to a new server and hopefully could get a better result in your speed. Note that during a few hours in a day, we have peak times. That means our servers are overloaded and the number of online users is high. In these situations, you have 2 options: Keep trying to connect or re-connect Betternet a few minutes later.